The singer and model has been a permanent member of the judging panel on the singing show since 2012 but, according to reports, is expected to leave to return to her music career.

Gary Barlow has already announced he is leaving, with former judge Cheryl Cole widely expected to return.

Veteran panellist Louis Walsh also said he was quitting, although he has indicated he might have had second thoughts.

Cowell announced last week he was returning for the next UK series of the show later this year.

The music mogul said he was "absolutely thrilled to be returning" and bosses will be hoping his reappearance will boost viewing figures.

He quit the UK panel to establish the series across the Atlantic, but US audiences have not met expectations and viewing figures at home have also slumped since he left, with the show regularly beaten by BBC rival Strictly Come Dancing.

For his last series in 2010, there was an average audience of 17.2 million watching Matt Cardle triumph, but by last year the climax of the series drew 9.7 million.

The show's finale in 2005 - which pulled in 9.3 million - was the only one to fare worse than that of last year.